dull rage

Senior Member

He started in, then thought better of it and stood where he was a moment longer, listening to her, not particularly caring about who she was talking to or what she said, only listening to the rising-falling tones of her voice. And what he felt was the old familiar dull rage.
<...>
The dull rage came again. His stomach filled with a heat which was not entirely unpleasant. Smoking. She was smoking.
Source: It by Stephen King

What does dull rage mean? Is it a rage that is muted? still under controlled?